Thermographic stencil sheet and method of making an imaged stencil sheet

ABSTRACT

A THERMOGRAPHIC STENCIL SHEET WHICH MAY BE IMAGED BY HEAT GENERATED BY INFRARED RAY ABSORPTION WITH BUT LOW OIL TRANSFER TO AN ADJACENT ORIGINAL INCLUDES AN INKPERVIOUS BASE SHEET AND AN INK-IMPERVIOUS COATING THEREON OF A HEAT-FLOWABLE COMPOSITION OF CELLULOSE ACETATE BUTYRATE FILM-FORMING MATERIAL AND PLASTICIZING MATERIAL PARTIALLY BUT INCOMPLETELY COMPATIBLE WITH THE FILM-FORMING MATERIAL, THE COMPOSITION BEING CHARACTERIZED BY FORMING A COOLED MELT HAVING A DEFINED POURABLE LIQUID VOLUME, AND THE PLASTICIZING MATERIAL BEING CHARACTERIZED BY DEFINED TACK AND ANILINE POINT LIMITS. THE STENCIL SHEET MAY BE IMAGED BY EXPOSING AN ORIGINAL IN CONTACT WITH THE SHEET TO INFRARED RADIATION TO GENERATE HEAT IN THE IMAGE AREAS OF THE ORIGINAL SUFFICIENT TO RENDER THE COMPOSITION FLOWABLE IN THE IMAGE AREAS OF THE STENCIL SHEET, AND CAUSING THE COMPOSITION TO FLOW FROM THE IMAGE AREAS TO THEREBY FORM CORRESPONDING INK-TRANSMITTING OPENINGS IN THE STENCIL SHEET.

United States Patent 3,704,155 THERMOGRAPHIC STENCIL SHEET AND METHOD OFMAKING AN IMAGED STENCIL SHEET Bror E. Anderson, Arlington Heights, andMargery L.

Schick, Mount Prospect, 11]., assignors to Weber Marking Systems, Inc.,Arlington Heights, Ill.

No Drawing. Continuation-impart of application Ser. No. 674,153, Oct.10, 1967. This application Apr. 9, 1970, Ser. No. 27,135

Int. Cl. B41m 1/24 US. Cl. 117-355 Claims ABSTRACT OF THE DISCLOSURE Athermographic stencil sheet which may be imaged by heat generated byinfrared ray absorption with but low oil transfer to an adjacentoriginal includes an inkper'vious base sheet and an ink-imperviouscoating thereon of a heat-fiowable composition of cellulose acetatebutyrate film-forming material and plasticizing material partially butincompletely compatible with the film-forming material, the compositionbeing characterized by forming a cooled melt having a defined pourableliquid volume, and the plasticizing material being characterized bydefined tack and aniline point limits. The stencil sheet may be imagedby exposing an original in contact with the sheet to infrared radiationto generate heat in the image areas of the original sufiicient to renderthe composition fiowable in the image areas of the stencil sheet, andcausing the composition to flow from the image areas to thereby formcorresponding ink-transmitting openings in the stencil sheet.

RELATED APPLICATION This is a continuation-in-part of application Ser.No. 674,153, filed Oct. 10, 1967.

BACKGROUND OF THE INVENTION This invention relates to a thermographicstencil sheet of the type which includes a layer of a heat-flowablecomposition and to a method of making an imaged stencil sheet therewithby subjecting image areas of the stencil sheet to heat generated byinfrared ray absorption.

Our copending US. patent application Ser. No. 674,153, filed Oct. 10,1967 now abandoned, discloses a thermographic stencil sheet including anink-pervious base sheet and an ink-impervious coating thereon of aheat-fiowable composition of cellulose acetate butyrate film formingmaterial and plasticizing material partially but incompletely compatiblewith the film-forming material. The stencil sheet is now in widespreadcommercial use. It is employed preferably in a stencil sheet assemblyincluding a contacting absorbent sheet on one surface thereof, and amore rigid backing sheet on the opposite surface thereof and to whichthe absorbent sheet and the stencil sheet are mounted. In use, anoriginal, such as a typed or printed sheet, is inserted between thestencil sheet and the backing sheet, and the assembly is exposed toinfrared radiation on the face side of the absorbent sheet in a thermalcopier such as a Thermo-Fax machine (3M Company). Heat is generated inthe radiation absorptive graphic portions of the original to cause thestencil sheet composition to flow in corresponding areas and therebyproduce corresponding image openings in the stencil sheet. Thecomposition rendered fiowable is absorbed by the absorbent sheet and/oradjoining areas of the stencil sheet. The original and the absorbentsheet are separated from the imaged stencil sheet, the stencil sheet andthe backing sheet are placed on a mimeograph duplicating machinefollowed by separation of the backing sheet, and the machine is operatedto produce multiple mimeograph copies of the original.

It was found in use that oil was transferred from the stencil sheet tothe original in the image areas. The oil frequently broadened andfeathered the copy on the original (smudging) and the presence of oil onthe original was not a desirable condition. The smudging of the originalaffected the imaging speed in subsequent exposures, owing to thebroadening of the imaged characters or transfer from the original to thestencil sheet. Subsequent performance was affected when the original wasremoved from the file for rerun, or in the event that optimum exposurewas not used in imaging the first stencil.

It would be desirable to reduce the oil transfer to acceptable limitswhile preserving the advantageous properties of the stencil sheet of ouraforesaid copending application.

SUMMARY OF THE INVENTION The present invention provides a thermographicstencil sheet of the type disclosed in our aforesaid copendingapplication which exhibits low oil transfer while maintaining and inmany cases improving on copy quality. The stencil sheet includes aheat-fiowable composition characterized by forming a cooled melt havinga defined pourable liquid volume, and a plasticizing material in thecomposition characterized by defined tack and aniline point limits.

More particularly the thermographic stencil sheet of the presentinvention comprises an ink-pervious base sheet, and an ink-imperviouscoating thereon of a heatfiowable composition of cellulose acetatebutyrate filmforming material, and plasticizing material having (a) atack index, as defined hereinafter, of at least about 10, and (b) amaximum mixed aniline point of about F., the said composition initiallyforming a clear homogeneous single phase melt at a maximum temperatureof about 320 F. and forming a solid-liquid twophase mixture when cooledfrom the melt to room. temperature, at least one phase of the saidmixture incorporating substantial proportions of both the film-formingmaterial and the plasticizing material, the mixture having a pourableliquid volume which is a. maximum of about one-fourth the volume of thesolid phase, the said composition being soluble in a volatile solventand forming a substantially clear homogeneous continuous imperforatecoating when deposited from a solution thereof, and the said coatingbeing provided on the base sheet by deposition of the composition on thebase sheet from a solvent solution thereof, the melting point of thecoating being in the range of about -320 F.

The invention also provides a method of making an imaged stencil sheet,wherein the thermographic stencil sheet is employed in contact with agraphic original, image areas of the stencil sheet are subjected to heatgenerated in the original by infrared ray absorption to render thecomposition flowable in the stencil sheet image areas, and thecomposition is caused to flow from the image areas and thereby formcorresponding ink-transmitting image openings in the stencil sheet.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The thermographic stencil sheetincludes a stencil base tissue sheet that may be formed of any suitablefiber, such as abaca and wood fibers, kozo fiber, or polyester fibers,loosely arranged to provide a foraminous, highly permeable tissue. Thetissue may weigh about four and one-half to twelve pounds per 3,000 sq.ft. (24" x 36", 500 sheets).

3 A heat-flowable coating composition, which is solid at ambienttemperature, is applied to the base sheet at a rate of about 14 to 24lbs. (dry basis), preferably about 20 lbs. per 3,000 sq. ft. The coatingcomposition melts in the range of about l50-320 F., more preferably200-300 F.

The heat-flowable coating composition includes cellulose acetatebutyrate film-forming material, which is ca pable of forming acontinuous, cohesive, flexible, ink-impervious film. The film-formingmaterial is plasticizable to melt in the range of about 150-320 F. Thefilm-forming material is employed in a proportion in the range of about8-50%, preferably about 830%, and more preferably about 14-23% by weightof the coating composition, including the film-forming and plasticizingmaterials and exclusive of additives thereto. The volume ratio of thefilm-forming material to the total plasticizing material in the coatingcomposition preferably is in the range of about 1:13 to 1:35.

Of the available grades of cellulose acetate butyrate, it is preferredto employ those having values of about 35-55% butyryl content, morepreferably above about 49%, and about 15-13% acetyl content, by weight.The hydroxyl content varies up to about 4.5% by weight, and it ispreferred that the hydroxyl content be below about 0.4%. The viscosityis about 0.15-6 seconds, by A.S.T.M. Method Dl343-54T in Formula A,A.S.T.M. Method D-87l-54T. The melting or softening points range fromabout 265 to 360 F.

The film-forming material is combined in the coating composition with aplasticizing material partially but incompletely compatible therewith.Such plasticizing material is defined to mean material which when heatedwith the film-forming material in the proportions used forms a clearhomogeneous single phase melt, and which when cooled from the melt toambient or room temperature forms a two-phase mixture, at least onephase of the mixture incorporating substantial proportions of both thefilm-forming material and the plasticizing material. The materialsemployed in the composition initially form a single phase melt at amaximum temperature of about 280-320 F., varying with the specificcomposition. Such temperature is referred to as the compatibilitytemperature of the composition. It is preferred that the compatibilitytemperature be at least about 120 F., and in further preferredembodiments of the invention, the compatibility temperature is aboveabout 170 F.

Upon cooling below the compatibility temperature, the liquid separatesinto two phases. The mixture remains fluid over a temperature range, andthen the phase containing the major proportion of the film-formergradually hardens to a solid as the coating cools to room temperature.The liquid phase may be trapped by the gel structure of the solid phaseat room temperature, or it may separate into a discrete liquidcomponent.

A characteristic of the present invention is that the foregoing mixtureat room temperature has a maximum pourable liquid volume of aboutone-fourth the volume of the solid phase, and it is preferred that thepourable liquid volume be a maximum of about one-eighth the volume ofthe solid phase. For example, the mixture is cooled to room temperaturewith stirring, and its consistency is observed. A uniform gel or slush,having no solid separation, generally is optimum for low oil transfer.The mixture may separate into solid and liquid fractions, the solidbeing particulate or in the form of a ball, from which a liquid may bepoured. It is the volume of such pourable liquid with reference to thesolid content of the mixture which is referred to in connection with theabove pourable liquid volume maximums.

The plasticizing material having partial but incomplete compatibilitywith the film-forming material may constitute a single plasticizer, ormay include a plurality of plasticizers. The plasticizers aresubstantially nonvolatile substances which serve to modify the physicalproperties of the film-forming material, including the melting orsoftening point, compatibility, and/or flow properties. They may beeither liquid or solid at temperatures from ambient temperature up toclose to imaging temperature, but at least must be liquid when mixedwith other plasticizers at imaging temperature.

The plasticizers generally fall into three groups as regardscompatibility with the film-forming material: partially but incompletelycompatible, incompatible, and compatible substances. Certain of thepartially compatible plasticizers may be employed as sole plasticizers.Alternatively, two or more plasticizers having individualcompatibilities varying from complete compatibility to completeincompatibility may be employed, so long as the plasticizers togetherprovide the proper balance of compatibility with the film-formingmaterial. When a plurality of plasticizers is employed, it is preferredthat they be compatible with each other at room temperature, forming asingle phase mixture after heating together and cooling.

The above-described characteristic composition having the definedmaximum pourable liquid volume constitutes a relatively compatiblecomposition. When such a composition is employed in the stencil coating,the coating may suffer from blocking, owing to tackiness accompanyingincreased compatibility. Blocking is a condition of adherence orsticking to adjacent stencil material in a roll, or sticking to theoriginal or the top tissue during imaging, which causes pinholing. Wehave found that plasticizing material can be formulated on the basis ofdefined tack limits to minimize blocking. In particular, a plasticizingmaterial, including one or more plasticizers, is employed which has atack index of at least about 10, determined as follows:

The Tack Rolling Ball Method of the Pressure Sensitive Tape Council(Glenview, Ill.) was modified for a lower tack level, and the modifiedmethod is identified herein as the modified rolling ball method. Theapparatus included a glass plate, 8 /2" x 11" supported in horizontalposition. A second glass plate, 3" x 6", was mounted with its 3" edgeabutting the 8 /2" edge of the first plate, with their upper edges orcorners in aligned contact with each other. A ball holder was affixed tothe smaller plate to release a ball /2" from its outer end. The outerend of the smaller plate was elevated so that the surface of the plateat the point of ball release was 0.203" above the horizontal plane ofthe upper surface of the large plate. The apparatus thus was arrangedfor releasing a steel ball on the small plate to roll down 5 /2 of thesmall plate and on to the large plate. Steel balls were used having adiameter of and weighing 5.48 grams.

In the test, a film of the plasticizing material to be tested is cast onthe large plate and drawn down to a thickness of /2 mil. The film iscast at a temperature such as to render the plasticizing materialsufficiently fluid, and is cooled, if necessary, for measurement at roomtemperature (77 F.). The cast film is drawn down with a rod or othersuitable means to provide the film thickness of /2 mil.

A ball rolling across the film will experience a decelerating forceproportional to the velocity of the ball and the tackiness of the film.Liquid viscosity also has an effect, minimized by employing the verythin film. In addition, an experimentally determined viscosity factor isapplied to the results.

Tack measurements are made in inches of ball roll on the larger platebearing the film, measured to the point the ball stops. The tackier thematerial, the shorter the distance of ball roll. The tack index referredto herein and in the claims is determined by measurement of the amountof ball roll on the horizontal plate, in inches, multiplied by the logof the viscosity of the plasticizing material in centipoises at 77 F. Inthe invention, such index is at least about 10.

The above-described conditions of maximum poura-ble liquid volume from acooled melt of the composition of film-forming and plasticizingmaterials, and of a minimum tack index will in general serve to identifythe coating compositions, both in their materials and in their relativeproportions, which will provide low oil transfer with minimizedblocking. There are, however, exceptions, and it is found in theinvention that the exceptions noted are excluded by limitations on theaniline point of the plasticizing material, the aniline point serving asan indication of the compatibility of the plasticizing material with thefilm-formng material. Thus, the plasticizing materials employed in theinvention are relatively compatible with the film-forming material,while remaining partially but incompletely compatible therewith. Ingeneral, a maximum mixed aniline point of about 110 F. is specified forthe plasticizing material. In a specific embodiment of the in vention,described hereinafter, it has also been found that oil transfer isreduced in the presence of an aluminum stearate gelling agent. In suchcase, the maximum mixed aniline point may be about 110135 F.

Mixed aniline point as referred to herein and in the claims isdetermined by A.S.T.M. test D10l2-62. It is the minimum equilibriumtemperature of a mixture of 2 volumes of aniline, 1 volume of sample,and 1 volume of n-heptane of specified purity. Straight aniline point isdetermined according to the A.S.T.M. test, and is the minimumequilibrium temperature of a mixture of 1 volume of aniline and 1 volumeof sample. For formulating purposes, it is generally useful to mix highaniline point material with a low aniline point, low tack material suchas Hercolube A (described hereinafter), in a 50:50 volume ratio, and runthe aniline point of the mixture. Similarly, it is useful to mix lowaniline point material With high aniline point material such asMo'bilsol L (described hereinafter). Theoretical aniline points may bedetermined in this manner for materials which otherwise cannot bemeasured or can be measured only With difficulty. Theoretical anilinepoints referred to hereinafter were determined in the foregoing manner.

The plasticizing material and proportions thereof are selected on thebasis of the herein-defined physical properties. Numerous and diversematerials may be employed, in a variety of combinations and relativeproportions. Most frequently, a plurality of individual plasticizers arecombined to achieve the specified physical conditions and optimumresults. When the plasticizing material satisfies the basic conditions,the proportions of individual plasticizers thereof then may be adjustedWithin the defined limits to achieve optimum properties.

The plasticizing material is oleaginous or oily in nature that is, itcontains one or more oleaginous plasticizers. While numerous oleaginousplasticizers may be employed, it is presently preferred to employ one ormore members selected from the group consisting of mineral oil, castoroil, hexadecyl alcohol, polypropylene glycol monobutyl ether,polyoxyethyelne others or lanolin alcohols, pentaerythritol tetra-estersof aliphatic acids having from 5 to carbon atoms, and trimethylolpropane tri-esters of aliphatic acids having from 5 to 10 carbon atoms.An oleaginous plasticizer or mixture of plasticizers may be present in aproportion in the range of about 585% by weight of the film-formingmaterial and plasticizing material, such materials being referred toherein as the active materials, excluding materials which are neitherfilmformers nor plasticizers, such as inert solids and other materialsperforming other functions.

It is further preferred to employ plasticizing material containingmineral oil, an ester of an aliphatic acid having from 5 to 10 carbonatoms, as described above, or a mixture of the two. The mineral oilpreferably is employed in a proportion of about 5-70% by weight of thecomposition of film-forming material and plasticizing material, morepreferably, 10 to 50%. The aliphatic acid ester is employed in aproportion of about 5-85% by weight of the composition, preferably15-55%.

A valuable class of plasticizers generally employed with one or moreother plasticizers in the invention constitutes materials having anucleus selected from the group consisting of and I such materialsprovide low oil transfer and/ or low tackiness properties. They may beemployed in proportions of about 5-75%, preferably 15-55% by weight ofthe filmforming and plasticizing materials.

The materials having the foregoing nucleus include lanolin sterols,which serve to impart low tackiness.

The materials including such nucleus also include the acid constituentsof rosin, known as resin acids, and their derivatives, includingderivatives of the resin acids both in refined form and as present inrosin, about of which constitutes resin acids. The resin acids arechiefly the abietic acid type, and abietic acid is the major constituentof the acids. The resin acid derivatives are preferred as having greaterstability than the resin acids.

Preferred derivatives of the resin acids include hydrogenated resinacids, esters of hydrogenated resin acids, esters of resin acids,hydroabietyl alcohol, and esters of hydroabietyl alcohol. Preferredesters include the methyl, pentaerythritol, glycerol, phthalate, andpolyol esters, the latter including particularly the diethylene andtriethylene glycol esters. Such materials are in general relativelycompatible with the film-forming material and with other plasticizers,and they serve to impart low oil transfer and/or better durability tothe coating composition, partially as a result of the higher viscositythey impart.

A formulation for high viscosity may assist valuably in the provision ofa low oil transfer composition. With higher viscosity, compatibility ofthe plasticizing material with the film-forming material may be andoften preferably is reduced with the aniline point of the plasticizingmaterial being higher. Also, the tackiness of the plasticizing materialmay be higher, and the pourable liquid volume from the cooledcomposition melt may be greater. However, the copy quality may suffer insome cases.

The film-forming and plasticizing materials of the coating compositionare soluble in a volatile solvent and are selected and blended inproportions so as to form a substantially clear homogeneous continuousimperforate coating when deposited from a solution thereof, the coatingthen being provided on the base sheet by deposition of the compositionthereon from such solution. In this connection, reference to clarity ofthe coating, as an index of compatibility, is to be understood as beingexclusive of the effects of additives other than the active or basicfilm-forming and plasticizing materials, i.e., additives such as solidsincorporated for other purposes, fillers and others. Reference toclarity is also exclusive of the opacifying effects of materials havingan inherent opacity, such as waxy materials, and of the presence ofmaterials which are solid at room temperature and are incorporated abovetheir solubility limits at room temperature.

The coating composition preferably is completely soluble in a volatilesolvent at a temperature below about F., more preferably, at roomtemperature. The preferred coating compositions are soluble in organicsolvent mixtures of aromatic hydrocarbons, and aliphatic esters and/oraliphatic alcohols, and are deposited on the base sheet from a solutiontherein by evaporation of the solvent. The composition deposited in thismanner forms a uniform gel on the base sheet, which is irreversiblyphysically altered when heated to its melting point.

The film-forming and plasticizing materials are selected and blended inproportions so as to form a stencil sheet coating melting in the rangeof about ISO-320 F. The stencil coating may melt at a temperature frombelow to above the compatibility temperature, described above.

Reference to the melting point of the coating herein means thetemperature at which a free film of coating on a vertical surfacebecomes liquid enough to flow. (A free film is obtained by depositingthe coating from solvent onto a non-porous surface.)

For optimum results, it may be necessary to adjust the ingredients ofthe coating composition and their propertions on the basis of observedresults. That is, adjustment may be made to improve uniformity,featherness, and brokenness of the imaged characters, oiliness,blocking, speed of imaging, and durabiliy. The majority of the stencilsheets illustrated herein may also be imaged mechanically, as by typing,which constitutes a substantial advantage. Adjustment of the materialsand proportions also may be made to provide optimum typing sensitivity.

The stencil sheet may be imaged in a conventional thermographic machine,such as a roller-type copier as represented by Copy-Rite Model CF 8(Polyfax Corporation), and a belt-type copier such as a Thermo-Fax Model45CG Secretary machine. A tungsten filament lamp or other suitablesource of infrared radiation is employed for imaging. A printed originalin contact with the stencil sheet is exposed to radiation substantiallyinstantaneously, i.e., on the order of about 0.03 to 0.1 second, togenerate a temperature rise in the image portions of the original fromabout ambient temperature to a temperature sufiicient to produce atemperature in the image portions of the stencil sheet in the range ofabout ISO-320 F.

The coating composition in the stencil sheet is reduced to a flowablecondition substantially instantaneously and is absorbed by the absorbentsheet or into adjacent areas of the stencil sheet immediatelythereafter, to leave ink-transmitting image openings in the stencilsheet. The openings are bridged by the fibers of th stencil base sheet,which is ink-previous, and the base sheet fibers serve to retain lettercenters and the like in place. The imaged stencil sheet is separatedfrom the original and the absorbent sheet for use as a duplicatingmaster.

An advantageous additive to the composition of filmforming andplasticizing materials satisfying the above conditions is a gellingagent for the plasticizing material, forming an irreversible gel uponheating up to about 210 F. Especially low oil transfer is achieved inthis manner. This embodiment is preferably employed when the stencil isintended for use on roller type thermal copiers, whereas it is not welladapted for the belt-type copiers. It appears that the superiority ofthe roller type copiers is due to the good contact of the stencil withthe original and the pressure exerted on the stencil at the time ofimaging, serving to remove fiuid from the image areas.

The preferred gelling agents are the aluminum stearates. While variousgrades will provide improvement, aluminum distearate of the type thatgives highest gel strength is preferred. The stearates preferably areemployed in a proportion of about 1-15%, preferably 8- 11% by weight ofthe composition including film-forming and plasticizing materials, andstearate.

Employing an aluminum stearate gelling agent, the maximum mixed anilinepoint of the plasticizing material may be greater, in the range of about110-135 F., increasing in said range with increasing proportion of thegelling agent. The use of the gelling agent also is more broadlyapplicable to other coating compositions within the scope of ourapplication Ser. No. 674,153, inasmuch as the pourable liquid volume andthe tack index conditions no longer need be met.

In the examples which follow, the coating compositions were dissolved inone of several solvent mixtures, identified as follows:

GRAMS OF SOLVENT PER GRAMS ACTIVE MATERIALS The materials of eachcoating composition were dissolved at a concentration of about 30-35% byweight in the solvent mixture. The materials were mixed at roomtemperature, with a solution of the cellulose acetate butyrate beingadded last. Stencil base tissue sheet material made of abaca fiber wascoated and impregnated with the solution. The tissue weighed 6.7 lbs.per 3,000 sq. ft. The sheet material was coated with the solution bypassing it over a roll carrying the solution, removing excess fluid by adoctor rod, and drying with circulated air heated up to about F. Thetotal coated weight of the resulting stencil sheet ranged from 25.5 to28 lbs. per 3,000 sq. ft. The thickness of the resulting stencil sheetwas about 2% mils.

In addition to the listed ingredients, each coating composition included0.17 gram of an antioxidant per 100 grams of active materials, theantioxidant being Carstab DLTDP, described hereinafter.

Each stencil sheet was assembled with an absorbent sheet for imagingtests. The absorbent sheet was 10 lb. per 2,880 sq. ft. tissue formed ofmixed abaca and wood pulp fibers (Grade 55 tissue, Dexter Corporation).Oil transfer and image smudging was determined on carbon ribbon copytyped on bond paper and on offset printed stock. Blocking was determinedby storing unassembled stencil sheets in contact with each other infoil, at room temperature. Blocking was also determined in most cases byevaluating pinholing upon exposure with a blank sheet of paper in athermal copier. Durability was determined on a label printer type ofmimeograph stencil duplicating machine.

Materials which may be employed in the invention, and referred toherein, are described as follows:

CAB 500-1 is cellulose actate butyrate grade EAB 500-1 (Eastman ChemicalProducts) having an average butyryl content of 49.6%, an average acetylcontent of 5.5%, a hydroxyl content of 0.15-0.36%, a viscosity of0.8-1.2 seconds determined by the hereinabove-identified A.S.T.M.method, and a melting point range of about 329-347 -F.

CAB 451-1 is cellulose acetate butyrate grade EAB 451-1 (EastmanChemical Products) having an average butyryl content of 44%, an averageacetyl content of 8.5%, an average hydroxyl content of about 1.3%, aviscosity of 1-2 seconds by the A.S.T.M. method, and a melting pointrange of 302-311 F.

'Carstab DLTDP (Carlisle Chemical Works) is dilauryl thiodipropionate.

Mobilsol L (Socony Mobil Oil Co.) is a refined naphthenic petroleum oilhaving a viscosity of 61 Saybolt Universal Seconds (SUS) at 100 R, ananiline point of F. (straight, A.S.T.M. test D-1012-62), an API gravityof 25.7, and a distillation range of 490-708 F. (100%).

Compressor Lube 1500 (Witco Chemical Co.) is a highly paraffinic whitemineral oil having typical viscosities of 1537 SUS at 100 F. and 95 SUSat 210 F., and a specific gravity of 0.886. Its aniline point is greaterthan 230 F. (straight).

Hercolube A (Hercules, Inc.) is the mono-pentaerythritol tetra-ester ofcapric acid, having an acid num ber of 0.1, a saponification number of420, and a specific gravity of 1.002 at 25 C. It mixed aniline point is62 F.

MCP-42 (Mobil Chemical Co.) is a mixed tetra-ester of pentaerythritoland a mixture of aliphatic acids having -10 carbon atoms and an averagecarbon number of 6.9. The acids include -20% branched chain and thebalance straight chain alkanoic acids. The specific gravity is 1.00 atC. Its mixed aniline point is 42 F.

MCP-99 (Mobil Chemical Co.) is a mixed tri-ester of trimethylol propaneand a mixture of alphatic acids having 5-10 carbon atoms and an averagecarbon number of 8.3. The acids are straight chain alkanoic acids. Thespecific gravity is 0.985 at 25 C. Its mixed aniline point is 58 F.

Ucon LB-70-X (Union Carbide) is polypropylene glycol monobutyl etherhaving a viscosity of 70 centipoises at 100 F. Its mixed aniline pointis 77 F.

Ucon LB-300-X (Union Carbide) is polypropylene glycol monobutyl etherhaving a viscosity of 70 centipoises at 100 F. Its mixed aniline pointis 102 F.

Solulan 5 (American Cholesterol Products) is a polyoxyethylene ether oflanolin alcohols and contains lanolin sterols. It is a 5 mole ethyleneoxide ether of the lanolin alcohols. It typically has an acid number of3 max., a hydroxyl number of 120-135, a saponification number of 10max., and an iodine value of 20-30. Its mixed aniline point is less than40 F.

Modulan (American Cholesterol Products) .is acetylated USP lanolin asdescribed in U.S. Pat. No. 2,725,334. It typically has an acid number of3 max., a hydroxyl number of 10 max., a saponification number of 95-125,and a melting range of 40 C. Its mixed aniline point is 131 F.

Acetulan (American Cholesterol Products) is a liquid fraction ofacetylated lanolin alcohols typically having an acid number of 1 max., ahydroxyl number of 8 max., a saponification number of 180-200, an iodinenumber of 6-10, a specific gravity of 0.850-0.880 at 25 C., and aviscosity of about 10 centipoises at 25 C. Its mixed aniline point is F.

'Hercolyn D (Hercules, Inc.) is a hydrogenated methyl ester of rosinpurified by steam distillation, a liquid having a Gardner-Holdtviscosity at 25 C. of Z2-Z3 and an acid number of 7. Its mixed anilinepoint is 58 F.

Abitol (Hercules, Inc.) is technical hydroabietyl alcohol having aviscosity of 200 centipoises at 80 C., a specific gravity of 1.008 at 25C., a maximum acid number of 0.4, a maximum saponification number of 16,and a mixed aniline point of less than F.

Cellolyn 21 (Hercules, Inc.) is a phthalate ester of technicalhydroabietyl alcohol. It typically has an acid number of 8, asaponification number of 129, a specific gravity of 1.05 at 25 C., asoftening point (Hercules drop method) of 65 C., and a mixed anilinepoint of F.

Celloyln 104 (Hercules, Inc.) is a pentaerythritol ester of rosin,typically having an acid number of 30, a specific gravity of 1.13 at 25C., a softening point (Hercules drop method) of 101 C., and a mixedaniline point of 145 F.

Staybelite Ester 3 (Hercules, Inc.) is a triethylene glycol ester ofhydrogenated rosin, typically having a viscosity of 385 SUS at 100 F.,an acid number of 6, a specific gravity of 1.08 at 25 C., and a mixedaniline point of 61 F.

Staybelite Ester 5 (Hercules, Inc.) is 2. glycerol ester of hydrogenatedrosin purified by steam distilation, typically having a softening point(Hercules drop method) of 81 C., an acid number of 5, a specific gravityof 1.06 at 25 C., and a mixed aniline point of 85 F.

Staybelite Resin (Hercules, Inc.) is hydrogenated rosin, typicallyhaving a softening point (Hercules drop method) 10 of 75 C., an acidnumber of 165, a saponification number of 167, a specific gravity of1.045 at 25 C., and a mixed aniline point of 36 F.

Limited Poly-Pale Resin (Hercules, 'Inc.) is a reaction product ofpartially dimerized rosin and hydrated lime, typically having asoftening point of 175 C. (Hercules drop method), an acid number of 63,a specific gravity of. 1.10 at 25 C., and a mixed aniline point of 141F.

Flexalyn (Hercules, Inc.) is a diethylene glycol ester of rosin, havinga softening point (Hercules drop method) of 44 C., an acid number of 6,a specific gravity of 1.0 at 25 C., and a mixed aniline point of 76 F.

Pexate 510 E (Hercules, Inc.) is a high zinc content rosin-derivedthermoplastic resin having a softening point of 118 C., a specificgravity of 1.16 at 25 C., a zinc content as zinc of 10.1%, and a mixedaniline point of 109 F. (theor.).

Permalyn 330 (Hercules, Inc.) is a glycerol ester of stabilized resinacids, typically having a softening point of 87 C. (Hercules dropmethod), an acid number of 7, a specific gravity of 1.06 at 25 C., and amixed aniline point of 67 F. (theor.).

Surfactant -AR-150 (Hercules, Inc.) is a medium chain length ethyleneoxide adduct of rosin, typically having a viscosity of 400 centipoisesat 25 C., and a specific gravity of 1.099 at 25 C.

Halowax 1014 (Koppers Co.) is a mixture of pentaandhexachloronaphthalene having about 62% chlorine, a hard amorphous waxymaterial typically having a softening point of 137 C., a viscosity of 35SUS at 150 C., a maximum acid number of 0.05, and a specific gravity of1.78 at 25 C.

Halowax 1001 (Koppers Co.) is a mixture of triandtetrachloronaphthalenes having about 50% chlorine, a hard amorphous waxymaterial melting to a very mobile liquid at 90-95 C., and having aviscosity of 30 SUS at C., a maximum acid number of 0.05, and a specificgravity of 1.58 at 25 C.

Aluminum stearate No. 23 (Witro Chemical Co.) is a distearate made bythe precipitation process from mixed fatty acids averaging 18 carbonatoms.

=Polyvis O (Cosden Oil and Chemical Co.) is polyisobutylene, an oilyliquid having an average molecular weight of about 400, a viscosity ofSUS at 100 F. and 42 SUS at 210 F., a specific gravity of 0.837 at 25C., and an anline point of 211 F. (straight).

Piccolastic A-S-O (Pennsylvania Industrial Chemical Co.) is polystyrenehaving an average molecular weight of 350, a ball and ring melting pointof 50 C., and a specific gravity of 1.04 at 25 C.

Piccoumaron 410L (Pennsylvania Industrial Chemical Co.) is a polyindeneresin having a softening point of 100 C., a bromine number of 12, a meltviscosity of 100 centipoises at C., and a mixed aniline point ofPlccovar 450 (Pennsylvania Industrial Chemical Co.) is an alkyl-aromaticthermoplastic hydrocarbon resin having a large number of cyclicmolecular structures. It has a softening point of 100 C., a maximum acidnumber of 1, a bromine number of 17, a melt viscosity of 100 centipoisesat C., a specific gravity of 1.05 at 25 C., and a mixed aniline point of116 F.

Estynox 408 is iso-octyl epoxy stearate (Baker Castor Oil Co.). It hasan iodine number of 2, a hydroxyl number of 4.8, a saponification numberof 138, a specific gravity at 25 C. of 0.92, a viscosity of 18centistokes at 25 C., and a mixed aniline point of 53 F.

The following examples illustrate various coating compositions accordingto the invention. It will be understood that the invention is notlimited to the examples, which are merely illustrative, or to thematerials, proportions, conditions, and procedures set forth therein. Inthe examples, the aniline points and viscosities refer to measurementson the plasticizer or mixture of plasticizers, and do not include thefilm-former or solvents.

1 1 EXAMPLE 1 The following coating composition was applied fromsolution in solvent No. 1 to stencil base tissue, providing a totalcoated weight of 28 lbs. per 3,000 sq. ft.:

Volume percent Parts by weight Mixed aniline point, F-.--

Viscosity, cps. at 77 F The following coating composition was depositedfrom solution in solvent No. 2 to provide a total coated weight of 27lbs. per 3,000 sq. ft.

Volume Parts by percent weight Material:

CAB 500-1 15.8 20.2 Acetulan 70. 66. 4 Compressor Lube 1500.. 14. 2 13.4Mixed aniline point, F 70 Viscosity, cps. at 77 F 14.5

Acetulan is a low tack material providing a low tack plasticizingmixture. Inasmuch as the Acetulan has a low viscosity, a high viscoscitymineral oil, Compressor Lube 1500 and a higher proportion of CAB 500-1are employed to maintain stencil durability.

Stencil durability was rated good, imaging speed very good, imagingquality good, oil smudging very good, oil transfer good, and blockingfair.

When cooled from a melt, the coating composition formed a soft gel, withno pourable liquid.

EXAMPLE 3 The following coating composition was deposited from solutionin solvent No. 3, to provide a total coated stencil weight 28 lbs. per3,000 sq. ft.:

Volume Parts by percent weight Material:

CAB 5004 14. 3 16.7 Hereolube A- 25. 9 25.9 Stabelite ester No. 5.. 25.927.5 Mobilsol L 34. 0 30. 2 Mixed aniline point, F 107 Viscosity, cps.at 77 F 180 The stensil durability was rated good; the imaging speed,fairly good; the imaging quality, very good; and the oil smudging, oiltransfer and blocking properties, fair to good.

The plasticizing material when tested had a tack index of 12.4. Whencooled from a melt, the coating composition was a viscous slush withsmall lumps, having no substantial amount of liquid which could bepoured from the solid.

EXAMPLE 4 The following coating composition was deposited from solutionin solvent No. 4, to provide a total coated weight of 28 lbs. per 3,000sq. ft.

Volume Parts by percent weight Material:

CAB 500-1. 14. 3 16. 9 Hercolube A 31. 4 31. 7 Abitol 13. 4 13. 8Cellolyn 21 5. 0 6. 6 Mobilsol L- 35. 9 32. 4 Mixed aniline point, F 107Viscosity, cps. at 77 F 48 The stencil durability was rated good; theimaging speed very good to excellent; the imaging quality very good toexcellent; the oil smudging good, and the blocking good.

When cooled from a melt, the coating composition. was a soft gel.

EXAMPLE 5 The following composition was deposited from solution insolvent No. 3, to provide a total coated weight Mixed aniline point, F

1 Exclusive of aluminum stearate.

The stencil durability was rated very good; the Imaging speed on aroller copier good; the imaging quality on a roller copier very good;and the oil smudging, oil transfer, and blocking very good. In theabsence of the stearate, oil smudging was fair and oil transfer verypoor.

Other grades of aluminum stearate that may be employed include Witcograde 22 G, having a specific gravity of 1.01 at 25 C., a free fattyacid content of 6.1%, and a softening point of 157 C., the fatty acidcontent averaging less than 18 carbon atoms. Another suitable grade isMallinckrodt grade AX. Both materials are distearates produced by theprecipitation method.

EXAMPLE 6 The following coating composition was deposited from solutionin solvent No. 1, to provide a coated weight of 27 lbs. per 3,000 sq.ft.:

The stencil durability was rated fair; imaging speed very good, imagingquality good; oil smudging very good; oil transfer good; and blockinggood.

EXAMPLE 7 The following composition was deposited from solution insolvent No. 5, to provide a total coated weight of 26.5 lbs. per 3,000sq. ft.:

Volume Parts by percent weight erial: CAB 500-1 14.3 15. 6 HcrcolubeA-.. 41. 0 38. 6

Halowax 1014 10.0 16.9 Cellolyn 21 5. 0 4. 3 Mobilsol L 29. 7 24. 6Mixed aniline point, F 102 Viscosity, cps. at 77 F 750 The stencildurability was rated good; imaging speed very good; imaging quality verygood, oil smudging and transfer good; and blocking very good.

13 14 The plasticizing matetrials were mutually soluble at acteristicsindicated that the Halowax 1014 functioned elevated temperatures, butwere found to contain undisas a plasticizer during imaging While actingat least parsolved Halowax 1014 at room temperature. All materialstially as a filler in the coating composition at room temwere soluble inthe solvent. The coated stencil had a perature.

white cast apparently due to Halowax 1014 present in 5 The followingExamples 8-12 show additional 'low excess of its compatibility with theremaining plasticizing oil transfer coating compositions according tothe invenmaterials at room temperature. The performance chartion,applied similarly to the preceding examples:

EXAMPLE 8 Example Number 8A 8B 8C 8D 8E Vol. Wt. Vol. Wt., Vol. Wt.,V01. Wt., Vol., Wt. percent parts percent parts percent parts percentparts percent parts Material:

CAB 500-1 14.3 16.3 14.3 16.7 14.5 16.7 14 3 16 9 14.3 16 8 Hercolyrl D22.05 22 11.2 11.4 21.2 21.5 21.2 21 4 Staybelite ester N0. 3 15. 0 16.2 Cellolyn 21 40. 1 41. 1 5. 2 7. 0 7. 3 Cellolyn 104 10.6 11. 7Hercolube A 31. 4 31. 2 25.4 25. 2 31. 4 31. 6 14. 7 14. 8 MOP 14. 7 14.3 MCP-QQ- 21. 2 21. 1 Mobilsol L 23. 20. 2 28. 1 24. 6 28. 3 24. 9 28. 125. 2 28. 1 25. 2 Mixed aniline point, F. 97 103 100 104 Viscosity, cps.at 77 F 11, 700 65 142 32 67 EXAMPLE 9 Example Number 9A 9B 9C 9D 9EV01. Wt. Vol. Wt., Vol. Wt., Vol. 15., Vol., Wt. percent parts percentparts percent parts percent parts percent parts Material:

CAB 500-1.. 14.3 17 14.3 16 8 14.3 16.1 14.3 15.8 14.3 16.1 Hercolyn D.57. 1 58.4 24 0 23. 6 21.2 20. 8 Cellolyn 21 5.0 5 1 Pexate 510 E 18. 921.0 18. 9 20.8 Permalyn 330 24. 8 25. 1 Hercolube A 57. 2 58 24. 0 23.1 27. 6 26. 3 25. 0 24. 1 Modu1an 28. 5 25 28. 6 24. 8 Halowax 100 6. 49. 8 Mobilsol L.- 18. 9 16.2 14. 4 12.1 28. 1 24. 1 Mixed aniline point,F. 86 82 92 Viscosity, cps. at 77 F.- 3, 775 500 5, 57

EXAMPLE 10 Example Number 10A 10B 10C 10D 10E Vol. Wt., Vol. Wt., V01.Wt., V01. Wt., Vol. Wt., percent parts percent parts percent partspercent parts percent parts Material:

CAB 500-1 15. 8 20. 3 14. 3 18. 3 14. 3 17. 0 14. 3 18. 0 CAB 451-1 14.3 16. 6 Hercolyn D Hercolube A Soiulan 5 Tridecyl alcoh Butyl stearatePolyvis 0- Mobilsol L Compressor lube 1500 14.2 13. 8 Mixed anilinepoint, 1 70 95 108 1 73 62 Viscosity, cps. at 77 F 290 497 11. 5

1 Theoretical.

EXAMPLE 11 Example Number 11A 11B 11C 11D 11E Vol. Wt., V01. Wt., V01.Wt., Vol. Wt., Vol. Wt., percent parts percent parts percent partspercent parts percent parts Material:

CAB 500-1 14. 3 18. 4 14. 3 17 14. 3 17 14. 3 18. 8 14. 3 17 Solulan 5-85. 7 81. 6 I Ucon LB- 85.7 83 Ucon LB-300-X 85. 7 83 Hexadecyl alcohol85. 7 81. 2 Castor oil. 85. 7 Mixed aniline point, F- 40 77 102 70 90Viscosity, cps. at 77 F-- 20 40 720 Example 12 Example number 12A 12B12C 12D Material, volume percent: CAB 600-1 Hercolyn D..- Gellolyn 21Hereolube A.- Mpbi 01 L Plccoumaron 410L- Piccovar 450 42. 85

Piccolastlc A-50- Other representative materials that may be employedsimilarly to Hercolube A, MCP-42, and MCP-99 in the foregoing examplesinclude the mono-pentaerythritol tetra-ester of valeric acid; the 89%mono-pentaerythritol, 11% di-pentaerythritol tetra-ester of caproicacid; the 89% mono-pentaerythritol, 11% di-pentaerythritol tetraester ofcaprylic acid; and the di-pentaerythritol tetraester of caproic acid, inthe same order of preference. Additional materials that may be similarlyemployed include trimethylol propane tripelargonate, mixed mono anddi-pentaerythritol tetra-esters of mixed -7, 0-8, and 0-10 alkanoicacids, and mixed monoand di-pentaerythritol tetracaprylate.

We claim:

1. A thermographic stencil sheet which comprises an ink-pervious basesheet, and an ink-impervious coating thereon of a heat-flowablecomposition of (a) a resinous thermoplastic film-forming materialcomprising cellulose acetate butyrate, and

(b) an oily, substantially non-volatile plasticizing material having atack index of at least about 10, and a maximum mixed aniline point ofabout 110 F., said plasticizing material being partially butincompletely compatible with said film-forming material, the amount of(a) being about 850% by weight based on the total amount of (a) plus(b),

said composition forming a homogenous single phase melt when heated andforming a solidliquid two-phase mixture when cooled from the melt toroom temperature, said composition having a minimum compatibilitytemperature of about 120 F., at least one phase of said mixtureincorporating substantial proportions of both said film-forming materialand said plasticizing material, said mixture having a maximum pourableliquid volume of about one-fourth the volume of the solid phase, saidcomposition being soluble in a volatile solvent and forming asubstantially homogeneous continuous imperforate coating when depositedfrom a solution thereof, and said coating being provided on said basesheet by deposition of said composition on the base sheet from a solventsolution thereof and removing solvent therefrom, the melting point ofsaid coating being at least about 150 F., said coating further becomingflowable and irreversibly physically altered when heated to its meltingpoint iior forming ink permeable image areas in the cooled stencilsheet.

2. A stencil sheet as defined in claim 1 wherein said plasticizingmaterial comprises a member selected from the group consisting ofmineral oil, hexadecyl alcohol, polypropylene glycol monobutyl ether,polyoxyethylene ethers of lanolin alcohols, pentaerythritol tetra-estersof aliphatic acids having from 5 to carbon atoms, and trimethylolpropane tri-esters of aliphatic acids having from 5 to 10 carbon atoms.

3. A stencil sheet as defined in claim 2 containing, in proportions byweight of said composition, about 5- 85% of said member selected fromsaid group.

4. A stencil sheet as defined in claim 1 wherein said plasticizingmaterial comprises a plurality of plasticizers including a plasticizerhaving a nucleus selected from the group consisting of CH3 CH3 and 5. Astencil sheet as defined in claim 1 wherein said plasticizing materialcomprises a plurality of plasticizers including a lanolin sterol.

6'. A stencil sheet as defined in claim 5 containing about 5-75% of saidlanolin sterol, in proportions by weight of said composition.

7. A stencil sheet as defined in claim 1 wherein said plasticizingmaterial comprises a plurality of plasticizers including a memberselected from the group consisting of hydrogenated resin acids, estersof hydrogenated resin acids, esters of resin acids, hydroabietylalcohol, and esters of hydroabietyl alcohol.

8. A stencil sheet as defined in claim 7 containing about 5-75 of saidmember selected from said group, in proportions by weight of saidcomposition.

9. A stencil sheet as defined in claim 1 including in said coating analuminum stearate gelling agent for said plasticizing material in aproportion of about 1-15% by weight based on the total amount of (a)plus (b) plus said gelling agent.

10. In a method of making an imaged stencil sheet employing athermographic stencil sheet which includes an ink-impervious layer of aheat-flowable composition, wherein image areas of the stencil sheet aresubjected to heat generated in adjacent image areas of an original byinfra red ray absorption to render the composition flowable in thestencil sheet image areas and the composition is caused to flowtherefrom and thereby form corresponding ink-transmitting image openingsin the stencil sheet, the improvement which comprises employing as saidstencil sheet the stencil sheet of claim 1.

References Cited UNITED STATES PATENTS 1,790,987 2/ 1931 Horii 117-3551,792,095 2/1931 Honii 117-355 2,808,777 10/1957 Roshkind 117-3613,062,675 11/ 1962 Sheltfo 117-355 3,120,611 2/1964 Lind 117-3613,177,086 4/1965 Newman et al l17-36.1 3,250,637 5/1966 Frasher et al.117-355 3,368,989 2/1968 Wissinger et a1. 1l7-36.1 3,446,662 5/ 1969Newman 117-36.1

MURRAY KATZ, Primary Examiner US. or. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3,704, 155Dated November 28, 1972 Anderson, Bror E0 and Inventofls) Schick,Margery L,

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 2, line 69: Insert after "as" -abaca,--;

5 12: Change "formng" to --formi ng-; 5 57: Change "polyoxyethyelne" to--=-polyoxyethy1ene-; 5 57: Delete "or" and insert in place thereof 744: Change "th". to the--;

7 44: Change "previous" to -pervious--;

8 52: Change :"ec'tate" to --acetate--;

9 5: Change "capric" to --cap roic--;

9 7: Change "it" to --its'--;

9 60: Change "Celloyln" to =-Ce11olyn--;

9 70: Change '.'distiletion" to -disti11ation--; 10 4: Change "Limited"to --=-Limed-;

10 7: Delete the period (0) following "of", at

V the end of line;

10 39: Change "Witro" to --Witco--;

10 46: Change "anline" to -ani1ine-;

11 42: After "1500" insert a comma 11 53: After "weight" insert -of--;

11 62: Change "stensil" to --si:enci1-; and 13 1: Change "matetrials" to--materials-.

Signed and sealed this 13th day of November 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. RENE D. TEGTMEYER Attesting Officer ActingCommissioner of Patents USCQMM-DC 60376-F'69 a: u.s. GOVERNMENT PRINTINGOFFICE 1959 o-ass-aaa.

Disclaimer 3,704,155.Bror E. Anderson, Arlington Heights and Morgen; L.Schick, a Mount Prospect, I11. THERMOGRAPHIC STENCIL SHEET AND METHOD OFMAKING AN IMAGED STENCIL SHEET. Patent dated Nov. 28, 1972. Disclaimerfiled Jan. 24,1974, by the assignee, Weber M arising Systems, I nc.Hereby disclaims the portion of the term of the patent subsequent toNov. 28, 1989.

[Official Gazette March 12, 1974.]

Corrected Disclaimer 3,704,155.B1-or E. Anderson, Arlington Heights, andMargery L. Schick,-

Mount Prospect, I11. THERMOGRAPI-HO STENCIL SHEET AND METHOD OF MAKINGAN IMAGED STENCIL SHEET. Patent dated Nov. 28, 1972. Disclaimer filed Jan. 24, 1974, by the assignee, Weber M ark-mg Systems, law. Herebydisclaims the portion of the term of the patent subsequent to Sept. 26,1989.

[Oyficz'al Gazette May 6, 1 975.]

